The invention relates to a method of controlling a circuit arrangement for an AC voltage supply of a plasma display panel (PDP), more particularly a sustain driver. PDPs are flat picture screens or televisions which are produced with the aid of plasma technology. Light is then generated by small gas discharges between two glass plates. In principle, small, individual plasma discharge lamps are driven via electrodes arranged horizontally and vertically. Considerable electronic circuitry is necessary for operating the plasma cells. The so-called sustain driver whose task is to supply trapezoidal AC voltages to the self-capacitances of the plasma cells takes up the largest surface area. The electrodes of the plasma cells are then connected to the outputs of two half bridges of a commutation circuit. The two outputs of the half bridges may apply the positive input voltage +U0, the negative input voltage −U0 or the zero voltage (short-circuit of the electrode terminals) to the electrodes of the plasma cells. The two half bridges are supplied with an auxiliary voltage which corresponds to 50% of the input voltage U0. For the cells to be ignited, a rapid change from the positive to the negative voltage and vice versa is to take place on the electrodes. For this purpose, the voltage output of a half bridge converter is alternately connected to the positive voltage pole, whereas the other voltage output is applied to the minus pole. In so far as the two transitions are directly consecutive, the voltage on the plasma cells changes very rapidly from a negative to a positive value of the input voltage U0. As a result, the cells are ignited. To avoid losses which arise during the direct charging and discharging of the capacitor of the plasma cell, the sustain driver is usually structured as a resonant switched-mode power supply in which the charging and discharging of the capacitor of the plasma cell takes place free of losses in principle. When this principle of resonance is realized and converted, the oscillation is attenuated because the coils, supply lines and semiconductor switches represent parasitic resistances. This leads to the fact that the voltage on the plasma cell does not completely jump to the input voltage or zero, respectively. In consequence, the bridge transistors are included in the circuit leading to the development of a loss-affected recharging or residual discharge. The currents linked with this are flowing with each recharging even when the plasma cells should not light up. The loss-affected recharging or residual discharge further causes problems with respect to the electromagnetic compatibility (EMV). The influence of the parasitic resistances is noticeable as a characteristic stage in the oscillation curve of the plasma voltage. Once the charging current for the capacitor of the plasma cell has reached its output value, thus substantially zero, the characteristic stage appears in the oscillation curve (here: jump from “substantially zero” to “zero” in the oscillation curve. Before the oscillation operation the two transistors of the half bridge are turned off so that a change of the voltage on the capacitor of the plasma cell can take place).
This known symmetrical commutation circuit can be easily manufactured as regards the circuitry. Therefore, it is an object of the invention to provide a method of controlling a circuit arrangement for the AC power supply to a plasma display panel which leads to a compensation of the losses caused by the parasitic resistances and to a reduction of the electromagnetic interference.